The correct pronunciation of Bacillariophyceae is:

bah-sil-ee-oh-fi-see-ay

Here's a breakdown:

* bah as in "bar"

* sil as in "sill"

* ee as in "see"

* oh as in "go"

* fi as in "fine"

* see as in "see"

* ay as in "say"

It's a bit of a mouthful, but with practice, you'll get it!